Hi~ I have a betta fish that also has only one side of his "flaring" area developed. His other side is very small. He also has a normal fin on his right side (same side as the healthy flaring area), and he has a smaller fin on his left side (same side as his very very small area that cannot flare more than maybe 2mm).

Starting tonight he has been unable to move his smaller fin on his left side and he only moves seldom. He stopped eating this evening because he is not moving towards his food. He is in a 5 gallon tank with a gentle filter, his water was changed 20% about 3 days ago. The water ph and ammonia levels are fine and the temperature is about 80 degrees. His eyes are clear.

I am not sure if he has fin rot on that one side or not because he is hiding in his little cave now, but while panicking earlier this evening I gave him some antibiotic just in case (which I know was probably not the right thing to do T_T)

Should I move him into a smaller tank so that he can reach his food? Please advise.

I'm very worried about my little guy and I hope that someone can help me.

I don't know much about bettas but trying to move him to a smaller tank with no decos but some stones could be helpful to check his problems, if you give always the same food maybe trying another food type?

People say they love bloodworms, yesterday I rushed to buy some and mine hated it T_T!.

Anyway! Try to get him to check him better, look at his fins if they are normal.

I'm not an expert not even a proper betta owner (I'm learning!) but this might help some while we wait for the experts to reply.

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